1. Field of the Invention
The present invention provides apparatus for aspirating and dispensing controlled amounts of liquid from a solid dispense block into receptacles, the apparatus including means for loading pipette tips designed for sealing on its outside diameter into internal cylinders within the dispense block head.
2. Description of the Related Art
U.S. Pat. No. 5,497,670 issued Mar. 12, 1996, the subject matter set forth therein invented by the inventor of the present invention, discloses an improved dispensing head apparatus including means for loading pipette tips carried by a pipette plate onto dispensing cylinders, the loading force being maintained during the apparatus operation cycle, thus ensuring a hermetic seal. The pipette tips are manually placed on the tip plate, the plate sliding within the dispensing apparatus.
Although the pipette tip plate holder described in the aforementioned patent provides many advantages when used with the apparatus described therein, there are certain disadvantages associated with its use. In particular, there is a possibility that the pipette tip slide plate may become contaminated. Most importantly, the pipette tip plate configuration is not easily adapted for robotics operation or automation.
U.S. patent application Ser. No. 08/751,859 filed Nov. 18, 1996, the subject matter set forth therein also invented by the inventor of the present invention, provides a self contained head dispensing apparatus similar to that disclosed in the aforementioned patent but modified to the extent that the pipette tip plate disclosed therein is replaced with a more conventional pipette tip carrier which is less expensive, is less likely to be contaminated and wherein the carrier is easily adapted for robotics operation or automation.
A microplate typically holding 96 wells with 9 mm on centers spacing in a 8 by 12 array is typically used with most dispense apparatus. The early prior art dispense devices started with one dispenser and moved in the X-Y direction 96 times to dispense into each of the 96 wells. Over time, dispense devices were added to include one row (8 or 12 wells per row) and then indexing either 8 or 12 times to fill the entire plate. A 96 dispense apparatus device to fill an entire plate at one time is disclosed, for example, in the '670 patent noted above.
The microplate has recently changed in design. Higher production speeds and larger storage libraries required higher density formats. The 96 well format with its 9 mm spacing has increased to 384 with 4.5 mm spacing. The 384 microplate has increased to 864 and now 1536 with 2.25 mm spacing. These different density plates have the same foot print (length, width).
In the dispensing method disclosed in the '859 application, a pipette that fits on the outside of a cylinder and tapers down to a small point is used. Most pipette dispensing systems are connected to the cylinder used in the dispensing head using an “O” ring to ensure a proper fluid seal from the pipette inside diameter (“ID”) to the cylinders outside diameter (“OD”). The typical pipette seals on its ID and therefore builds up the OD of the pipette. The typical OD is larger than 4.5 mm and therefore makes it difficult for use with higher density formats dispensing like 384 (4.5 mm spacing) since the 384 microplate has 4.5 mm spacing—therefore a pipette is to be used on the 384 format must have an OD that is smaller than 4.5 mm.
Prior art dispense devices, like the one disclosed in the '679 patent, use separate cylinders (one for each pipette), 96 total. This is the easiest way to connect to the pipettes ID. If a pipette is designed that seals on its OD, a new dispense head design is required. This would include sealing, loading, and stripping methods.
What is thus desired is to provide a new pipette design that allows sealing on its outside diameter with means of loading and stripping and to provide a new dispense apparatus that essentially comprises an integral solid block and which does not require discrete cylinders.